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gh-119247: Add macros to use PySequence_Fast safely in free-threaded build (#119315)

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Add `Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST` and
`Py_END_CRITICAL_SECTION_SEQUENCE_FAST` macros and update `str.join` to use
them. Also add a regression test that would crash reliably without this
patch.
This commit is contained in:
Josh {*()} Rosenberg 2024-05-22 17:45:34 +00:00 • committed by GitHub
parent 2b3fb767be
commit baf347d916
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4 changed files with 106 additions and 3 deletions
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22
Include/internal/pycore_critical_section.h
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@ -108,6 +108,26 @@ extern "C" {
_PyCriticalSection2_End(&_cs2); \
}
// Specialized version of critical section locking to safely use
// PySequence_Fast APIs without the GIL. For performance, the argument *to*
// PySequence_Fast() is provided to the macro, not the *result* of
// PySequence_Fast(), which would require an extra test to determine if the
// lock must be acquired.
# define Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST(original) \
{ \
PyObject *_orig_seq = _PyObject_CAST(original); \
const bool _should_lock_cs = PyList_CheckExact(_orig_seq); \
_PyCriticalSection _cs; \
if (_should_lock_cs) { \
_PyCriticalSection_Begin(&_cs, &_orig_seq->ob_mutex); \
}
# define Py_END_CRITICAL_SECTION_SEQUENCE_FAST() \
if (_should_lock_cs) { \
_PyCriticalSection_End(&_cs); \
} \
}
// Asserts that the mutex is locked. The mutex must be held by the
// top-most critical section otherwise there's the possibility
// that the mutex would be swalled out in some code paths.
@ -137,6 +157,8 @@ extern "C" {
# define Py_END_CRITICAL_SECTION()
# define Py_BEGIN_CRITICAL_SECTION2(a, b)
# define Py_END_CRITICAL_SECTION2()
# define Py_BEGIN_CRITICAL_SECTION_SEQUENCE_FAST(original)
# define Py_END_CRITICAL_SECTION_SEQUENCE_FAST()
# define _Py_CRITICAL_SECTION_ASSERT_MUTEX_LOCKED(mutex)
# define _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED(op)
#endif /* !Py_GIL_DISABLED */